Expose mdadm status in host/advanced

[olivierlambert]

We need to expose mdadm health info, leveraging the relevant XAPI plugin doing this.

Here is an example with xe:

$ xe host-call-plugin host-uuid=<uuid> plugin=raid.py fn=check_raid_pool
{"raid": {"Working Devices": "2", "Raid Devices": "2", "Raid Level": "raid1", "Creation Time": "Wed Jul 17 13:29:42 2019", "Used Dev Size": "52428672 (50.00 GiB 53.69 GB)", "UUID": "1766eb6e:85762159:4c98b42e:2da92c97", "Array Size": "52428672 (50.00 GiB 53.69 GB)", "Failed Devices": "0", "State": "clean", "Version": "1.0", "Events": "44", "Persistence": "Superblock is persistent", "Spare Devices": "0", "Name": "localhost:127", "Active Devices": "2", "Total Devices": "2", "Update Time": "Tue Jul 30 01:58:48 2019"}, "volumes": [["0", "8", "0", "0", "active sync", "/dev/sda"], ["1", "8", "16", "1", "active sync", "/dev/sdb"]]}

1. If the plugins reports {} it means there's no mdadm RAID, so it's not useful to even display anything
2. If there's something else than {}, for any State other than active or clean, we should provide a red/warning and display the state. If it's doable, it might worth a warning in the Home/host view, where we already have our alerts displayed.
3. Otherwise it's active or clean and comes with a "All mdadm RAID are healthy ✅"

Debouncing

We should debounce the plugin call as possible, there's no need to call it every load, once per 10min is far than enough for now